This invention relates to an apparatus for inserting coils and wedges into stator cores of dynamoelectric machines. In particular, this application relates to an apparatus for insertion of coils and wedges into lengthy stator cores, namely stator cores which have a relatively large stack height to bore diameter ratio.
A number of machines have been developed for inserting pre-wound coils and wedges into stator cores. In such machines the coils are generally formed by winding machines and are placed over an array of tooling blades or fingers for subsequent insertion into a stator core. Insulating wedges may be inserted by the same equipment to separate the windings from one another or to insulate the windings from the stator core.
In such machines, the wedge guides for guiding the wedges into the stator slots are arranged in a circular array and are supported by a housing. A moveable blade pack including a stripper and an array of blades is disposed inside the wedge guide array. After the coils have been draped over the blades, the blades are inserted into the bore of a stator core for insertion of the pre-wound coils into the stator core slots by means of relative axial movement of the stripper with respect to the blade array. Immediately following insertion of the coils into the stator core, the wedges are inserted into the slots of the stator core. During such wedge insertion, the wedges are guided by the wedge guides.
In the insertion of pre-wound coils into lengthy cores, the blades will need to travel a substantial axial distance and therefore may move completely out of the wedge guide array. Since the wedge guides are generally made of fairly thin metal, when the coil end turns are pulled tight during coil insertion, the wedge guides will be deflected inwardly toward the center of the circular wedge guide array once the blades have left the wedge guide array and therefore no longer support the wedge guides. Accordingly the wedge track formed by and located between the individual wedge guides through which the wedges are pushed into the slots of the stator core will no longer align accurately with the stator slots when the wedge guides are thus deflected. The stator core iron may therefore dig into the wedges as the wedges are inserted and may even stop the wedges from further movement. Accordingly less than complete insertion of the wedges may be encountered during such wedge insertion operations. If the deflection of the wedge guides is great enough, it is even possible that the entire coil insertion process may be stopped because of jamming of the apparatus.
An additional problem that occurs in such insertion operations is that the blade pack, consisting of the blades, the stripper and the blade holder, upon its retraction back into the wedge guide array, would interfere mechanically with the deflected wedge guides, therefore potentially causing severe wear of both the wedge guides and the blades. After a sufficient number of insertion cycles, the wear of both the wedge guides and the blades may be so extensive that they need to be replaced. Such replacement is relatively expensive because of the cost of providing accurately machined wedge guides as well as insertion blades.
The wedges normally are supported at two points during their insertion into a stator core. One end of each wedge is supported by the stripper during wedge insertion and the other end of each wedge is supported by a wedge guide support which is secured to and mounted below the blade holder. However, during the insertion of long wedges into lengthy cores the column strength of the wedges is not sufficient for the forces required to insert such long wedges. Accordingly, during insertion of such long wedges, the wedges will tend to buckle and will be forced into the steel laminations of the stator core. The wedges may even be forced out of the stator slots and into the stator slot entrances, thereby causing the wedge pushrods to partially destroy the wedges. The wedges may therefore no longer provide insulation for the coil wires of the assembled stator core. It is even possible that the buckled wedges may cause interference with the insertion process and therefore cause the apparatus not to fully insert the wedges or even to jam.
Thus it is desired to provide an apparatus wherein the wedges are supported at an intermediate point between their end points, to prevent deflection of the wedges during their insertion. Furthermore, it is desired to provide such an intermediate support which is automatically adjusted together with the stripper and blades during adjustment of the apparatus for insertion of coils and wedges into stator cores of various lengths.